Field of the Invention
The present invention relates to an automatic transmission for a vehicle. More particularly, the present invention relates to a planetary gear train of an automatic transmission for a vehicle that improves power delivery performance and fuel economy by achieving eight forward speed stages with a minimum number of constituent elements being used.
Description of Related Art
Recently increase of oil price is triggering a hard competition in enhancing fuel consumption of a vehicle.
Therefore, many researches for reducing weight and enhancing fuel economy through downsizing of an engine and for securing drivability and fuel economy through multiple speed stages of automatic transmissions have been developed.
However, in the automatic transmission, as the number of speed stages increase, the number of internal components increase, and as a result, mountability, cost, weight, transmission efficiency, and the like may still deteriorate.
Accordingly, development of a planetary gear train which may achieve maximum efficiency with a small number of components may be important in order to increase a fuel economy enhancement effect through the multiple-speeds.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.